Gunnar Thor Hallgrimsson emailed Cin-Ty and I some pics of the dowitcher found by Sigmundur Ásgeirsson and Ómar Runólfsson on 18 July. With only 7 Long-billeds and 0 Short-billeds, there's a lot of local interest in this bird and especially the bird potentially being Iceland's first Short-billed Dowitcher.
Have not heard Cin-Ty's opinion but to my eyes you can make out some rather pointed dark-centred lower scapular feathers amongst the worn alternate (summer) plumaged feathers.
Also, it's well marked flanks (mix of spotting and bars) is also typical of worn alternate Short-billeds in July and August unlike Long-billeds less-marked flanks. Structurally, it's rather drooping bill, shortish legs and less hunch-backed appearance also favor Short-billed.